Method of thickening a localized longitudinal element in a tube



6, 1946- s. WESTIN ETAL 2,405,478

METHOD OF THICKENING A LOCALIZED LONGITUDINAL ELEMENT IN A TUBE Filed Oct. 6, 1944 6 FIGJ. z 7

l7 Sven Wesi'in Axel westm INVENTORj.

ATTORNEY Patented Aug. 6, 1946 METHOD OF THICKENING A LOCALIZED LONGITUDINAL ELEMENT IN A TUBE Sven Westin, West Allis, and Axel Westin, Milwaukee, Wis., assignors to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of New York Application October 6, 1944, Serial No. 557,500

14 Claims.

This invention relates to a method of thickening a localized longitudinal element in a tubular blank. The invention employs the general principles of electro-fcrming set forth in U. S. Letters Patent No. 2,309,561 and may be employed in connection with various tube forming operations such as those set forth in U. S. Letters Patent No. 2,345,692 and in application, Serial No. 463,958, filed October 30, 1942, for Electric pipe forming, now Patent No. 2,371,090, dated March 6, 1945.

The general principles of electro-forming described in said patents and application involve the rotating of a blank in pressure contact with a plurality of circumferentially spaced electrodeforming dies wherein the blank is progressively heated to forming temperatures by resistance heating current flowing circumferentially through the blank in progressively adj acent circumferential segments thereof.

In these operations, the blank being continuously rotated relative to the electrode dies, there is a uniform heating and contraction in diameter of the blank throughout its circumference in the region of die contact therewith, and as the blank is moved axially into or through the dies it is progressively heated and formed in successive adjacent longitudinal regions.

The principal object of the invention is to provide a method for upsetting a localized longitudinal portion of a tubular blank.

Another object is to provide a method for simultaneously reducing a tubular blank in diameter and upsetting a localized segmental portion thereof.

The invention is carried out by varying the-time of heating of the various circumferential segmental portions of the blank by the circumferentially flowing heating current. This may be done in various Ways. For instance the blank may be given an oscillating or Varying speed rotary motion wherein one or more segmental portions of the blank are disposed to bridge the gap between the electrode dies for a longer period than do adjacent portions of the blank, or by controlling the heating current applied to the blank through the electrode dies in synchronism with the rotary movement involved so as to effect greater heating of a predetermined segmental portion or portions of the blank during forming.

The invention is illustrated in the accompanying drawing in which:

Figure 1 is a schematic side elevation, parts being shown in section, showing an apparatus for reducing a tube in diameter;

Fig. 2 is an enlarged transverse section through the blank on line 2-2 of Figure 1 and looking at the forming electrodes;

Fig. 3 is a longitudinal section through the electrode dies taken on line 3-3 of Fig. 2 and showing the forming operation;

Fig. 4 is a transverse section through the forming apparatus taken on line 4-4 of Fig. 3 and showing the segmental upsetting of the present invention;

Fig. 5 is a transverse section through the finished blank as it emerges from the forming dies, taken on line 5-5 of Fig. 3; and

Fig. 6 is a schematic side elevation similar to Fig. 1 and showing an electrical oscillator for carrying out the invention.

The apparatus illustrated includes the usual rotary chuck I for gripping the end of a tubular cylindrical blank 2 to be formed. The chuck I is mounted for horizontal movement by the piston 3 of a double acting hydraulic cylinder 4 for moving the same axially to feed the blank 2 longitudinally during forming operations.

The chuck l is rotated or oscillated by a motor 5 driving the speed reduction transmission 6.

The forming apparatus comprises two or more complementary circumferentially spaced electrode forming dies 1 and 8 having tapered die surfaces providing a substantially conicallyshaped die throat 9 through which the blank 2 is pushed by chuck I, the die throat being of somewhat smaller diameter than the blank.

The dies 1 and 8 constitute the opposite electrode terminals of a secondary transformer circuit H], the primary ll of the transformer being connected by leads [2 and switch I3 to a suitable source 4 of electric power.

In ordinary operations of reducing the blank 2 in diameter with a uniform wall thickness, the blank is rotated continuously at a constant speed as it is fed forwardly through the dies. The forward end of the blank first contacts the dies on the tapered or inwardly inclined die surfaces and as the heating current is applied it flows circumferentially through successive a jacent segmental portions of the blank bridging the circumferential gap between the electrodes until a circumferential or segmental band of the blank in the region of contact of the electrode dies becomes heated to a softened state. Thereupon the heated portion of the blank yields inwardly along the inclined die surfaces under the axial pressure of the feeding piston 3. This lengthens the pressure contact of the electrode dies and broadens the band of heating and forming until the blank a ed r78 progressively passes through the die th'roat 9 in reduced form.

According to the invention the above operations are modified in order to provide a greater heating effect, or to limit the heating effect to one or more predetermined segments of the blank whereby said segments will be upset greater than the intermediate or adjacent blank stock.

This may be accomplished in several ways. The speed of rotation of the blank may be varied to provide a low speed or dwell in a predetermined portion of the cycle of each revolution so that a given segmental part of the blank is subjected to a longer time of heating than the adjacent parts of the blank. Another way of accomplishing the varied heating is to oscillate the blank by alternate reversal in rotation, limiting the rotary movement in either direction short of a complete revolution.

For thin tubes where only a narrow upset is desired, it might be possible not to rotate the blank at all and to merely feed it into the die. Such an operation, however, would tend to extrude the upset portion radially outward in the space between the dies much as set forth in U. S. Letters Patent No. 2,345,692, bove referred'to.

In order to prevent outward extrusion of the upset portion and to obtain a product of circular outer contour it is desirable to maintain a semblance of rotary movement of the blank during forming. By doing this the upset l5 of the blank is provided on the inside as a thickened segment.

The actual width of the upset will depend upon the width. of the space between the electrode dies and the required amount of rotary movement of each oscillation or length of dwell employed to produce the same.

The various controls for the rotary movement desired may be provided in the transmission 6 which contains the reduction gearing and cranks cams for varying the speed of rotation or for effecting a predetermined stroke of oscillation of the chuck l.

Where a more narrow upset is desired than can be obtained in the manner above described, it is possible to limit the flow of heating current to a smaller segment of the blank by cutting on and off the heating current as shown in Fig. 6. In this modification the transmission 6 additionally contains a control switch [6 which interrupts the primary circuit I l of the transformer in synchronism with the rotary movement of the chuck i so that the heating current is applied to the blank only or mainly in the segment to be upset. In this way a better control of the heating and upsettting can be obtained.

If desired the differential heating may be obtained by this latter intermittent application of the heating current without varying the speed of rotation or oscillating the blank. When this is done the blank may be rotated continuously and at a uniform speed and the current cut on and off or varied during each revolution to give the desired heating of one or more segments. In this operation there may be some tendency for the upset segment of the blank to take the form of a spiral due to the twisting of the heated blank under torque loads in forming. The oscillating of the blank in alternate reversals of rotation avoids this.

Various embodiments of the invention may be employed within the scope of the accompanying claims.

part of said forming means to another part thereof in a circumferential direction, and selectively varying the time of heating to obtain a heating difierential between adjacent segments of the blank during shaping thereof.

2. The method of thickening a longitudinal segmental portion of a tubular blank while reducing the blank in diameter, comprising producing relative rotation and shaping pressure between the blank and a plurality f radially opposed electrode forming dies to simultaneously heat and shape the blank, and selectively heating adjacent segmental portions of the blank by regulating the relative heating current passing therethrough from said dies to obtain a heating differential therebetween.

3. The method of thickening a longitudinal segmental portion of a tubular blank while reducing the blank in diameter, comprising producing relative rotation and shaping pressure between the blank and a plurality of radially opposed electrode forming dies to simultaneously heat and shape the blank, and selectively heating adjacent segmental portions of the blank to obtain a heating differential therebetween by varying the speed of rotation of the blank relative to the electrodes in a predetermined cycle for each revolution.

4. The method of thickening a longitudinal segmental portion of a tubular blank while reducing the blank in diameter, comprising producing relative rotation and shaping pressure between the blank and a plurality of radially opposed electrode forming dies to simultaneously heat and shape the blank, and selectively heating adjacent segmental portions of the blank to obtain a heating differential therebetween by giving an oscillation of alternate reversals in direction of relative rotation between the blank and the electrodes.

5. The method of thickening a longitudinal segmental portion of a tubular blank while reducing the blank in diameter, comprising producing relative rotation and shaping pressure between the blank and, a plurality of radially opposed electrode forming dies to simultaneously heat and shape the blank, and selectively heating adjacent segmental portions of the blank to obtain a heating difierential therebetween by varying the heating current in a predetermined cycle for ach revolution of the blank relative to the electrodes.

6. The method of thickening a longitudinal segmental portion of a tubular blank while reducing the blank in diameter, comprising producing relative rotation and shaping pressure between the blank and a plurality of radially opposed electrode forming dies to simultaneously heat and shape the blank, and selectively heating adjacent segmental portions of. the blank to obtain a heating differential therebetween by reducing the time of the application of the heating current in the adjacent segments which are not to receive the maximum upset.

7. The method of thickening a longitudinal segmental portion of a tubular blank while reducing the blank in diameter, comprising producing relative rotation and shapin pressure between the blank and a plurality of radially opposed electrode forming dies to simultaneously heat and shape the blank, and selectively heating adjacent segmental portions of the blank to obtain a heating differential therebetween by applying the heating current only in the region of the segment or segments to be upset.

8. The method of treating a circular metallic body, comprising applying forming pressure to a plurality of opposed segmental areas in the region of forming of the body, transferring said forming pressure circumferentially to successive adjacent areas of the body in recurrent cycles, simultaneously therewith applying heat to suecessive adjacent segmental areas of said body intermediate th areas of pressure application, and selectively varying the application of heat to the body to elTect greater heating of one segment as compared to adjacent segments to thereby obtain a greater thickening of the same.

9. The method of treating tubular metallic bodies comprising applying shaping pressure to a body by a plurality of ciroumferentially spaced electrode dies which cooperate to supply a resistance heating current flowing circumferentially through the segmental portions of the body between the dies, relatively rotating said body and dies, and applying the heating current selectively to different segmental areas of the body.

10. The method of treating tubular metallic bodies comprising applying shaping pressure to a body by a plurality of circumferentially spaced electrode dies which cooperate to supply a resistance heating current flowing circumferentially through the segmental portions of the body between the dies, relatively rotating said body and dies, and altering the rotary movement to obtain a selective heating of different segmental portions of the body and efiect a thickening of the body in one or more segments.

11. The method of treating tubular metallic bodies comprising applying shaping pressure to a body by a plurality of circumferentially spaced electrode dies which cooperate to supply a resistance heating current flowing circumferentially through the segmental portions of the body between the dies, relatively rotating said body and dies, and altering the heating current for different segmental portions of the body to obtain a differential thickening of the body in adjacent segments thereof.

12. An apparatus of the class described, comprising a plurality of cooperating forming dies circumferentially arranged around a tubular blank to be electrically heated and formed, means to effect relative rotation between the blank and dies in radial pressure contact with each other, means to pass a heating current through the blank from one of said dies to another of said dies, and means connected with said first named means for selectively controlling the application of heating current to a predetermined segmental region of the blank differently from that of an adjacent segmental region and in co-relation to the relative rotation between the blank and dies.

13. An apparatus of the class described, comprising a plurality of cooperating forming dies circumferentially arranged around a tubular blank to be electrically heated and formed, means to effect relative rotation between the blank and dies in radial pressure contact with each other, means to pass a heating current through the blank from one of said dies to another of said dies, and means to alter th relative rotary movement between the blank and dies to increase the time of heating of a predetermined segmental region of the blank as compared to that of an adjacent segmental region.

14. An apparatus of the class described, comprising a plurality of cooperating forming dies circumferentially arranged around a tubular blank to be electrically heated and formed, means to effect relative rotation between the blank and dies in radial pressure contact with each other, means to pass a heating current through the blank from said dies, and means to alter the heating current to eiTect a selective control of the heating of a predetermined segmental region of the blank difierently from that of an adjacent segmental region.

SVEN WESTIN. AXEL WESTIN. 

